Saint-Petersburg Research Institute of Radiation Hygiene after Professor P.V. Ramzaev, Mira Str. 8, 197101 St.-Petersburg, Russia. Electronic address: V.Ramzaev@mail.ru.
Activity of biota is one of the factors influencing vertical migration of radionuclides deposited from the atmosphere onto the ground surface. The goal of this work was to study the vertical distribution of 137Cs in grassland soils disturbed by moles (Talpa europaea L.) in comparison with undisturbed grassland soils. Field observations and soil sampling were carried out in the areas of eight settlements in the Klintsovskiy, Krasnogorskiy and Novozybkovskiy districts of the Bryansk region, Russia in six years during the period 1999-2016. The study sites had been heavily contaminated by Chernobyl fallout in 1986. Activity of 137Cs in soil samples was determined by ?-ray spectrometry. 137Cs surface ground contamination levels at the studied plots (n?=?17) ranged from 327?kBq m-2 to 2360?kBq m-2 with a mean of 1000?kBq m-2 and a median of 700?kBq m-2. The position of the 137Cs migration centre in the soil in 2010-2016 was significantly (the Mann-Whitney U test, P?